1. Field of the Invention
The present invention relates to a magnetic recording medium used for a magnetic recording apparatus such as a magnetic disk apparatus and, more particularly, to an improvement in durability of the medium.
2. Description of the Prior Art
In a magnetic recording medium such as a hard magnetic disk for performing high-density recording, a metal magnetic thin film medium formed by, e.g., plating, sputtering, evaporation, has been used in place of a conventional coating type medium using a coating type magnetic film containing a magnetic powder and a binder.
When a recording/reproduction operation is performed with respect to a hard magnetic disk, in general, a CSS (contact start stop) system is used. In the CSS system, the disk is rotated at a predetermined speed, so that a very small air layer is formed between a magnetic head and the magnetic disk, and a recording/reproduction operation is performed in this state.
In the CSS system, the head is physically in contact with a surface of the magnetic disk in a stop mode. At the start and end of rotation, the head and the magnetic disk move relative to each other in a contact and friction state. The head and the magnetic disk surface are worn by friction at this time. When the head is brought into contact with the magnetic disk surface at high speed during a recording/reproduction operation, and large friction occurs between the head and the magnetic disk surface due to the presence of very small dust particles, the head or the magnetic film is often damaged.
In particular, in the metal magnetic thin film medium, since the coefficient of friction of the metal magnetic film is high, and the thickness of the film is small, the above problem is conspicuous. Therefore, in order to achieve corrosion resistance and lubricity of an upper portion of the metal magnetic film, a carbon protective film has been conventionally formed thereon. In addition, as shown in FIG. 3, a magnetic recording medium in which a liquid lubricant is coated on an upper portion of the carbon protective film has been used (e.g., Japanese Patent Laid-Open No. 61-208620).
An attempt has also been made to increase the coupling force between the lubricant and the carbon film using a liquid lubricant having a functional group (e.g., Japanese Patent Laid-Open No. 62-66417).
In the conventional magnetic recording medium shown in FIG. 3, however, the carbon film is insufficiently coupled to the lubricant. Therefore, when CSS is repeated, the effect of the lubricant is gradually reduced, and the friction force is increased. As a result, sufficient wear resistance and damage resistance cannot be obtained.
In addition, when the lubricant having the functional group is coated on the carbon film, it is strongly coupled to the lubricant. At the same time, the coupling force within the lubricant oil is increased. Therefore, the running property of the head is undesirably degraded.